Coated particles and sunscreen and cosmetic products containing same

Abstract

Particles have an ultrathin, conformal coating are made using atomic layer deposition methods. The base particles include ceramic and metallic materials. The coatings can also be ceramic or metal materials that can be deposited in a binary reaction sequence. The coated particles are useful as fillers for electronic packaging applications, for making ceramic or cermet parts, as supported catalysts, as well as other applications.

Description

CROSS-REFERENCE TO RELATED APPLICATION [0001] This application claims benefit of U.S. Provisional Application No. 60 / 810,362, filed Jun. 2, 2006, and of U.S. Provisional Application No. 60 / 843,445, filed Sep. 8, 2006.BACKGROUND OF THE INVENTION [0002] This invention relates to particulate materials that are useful as sunscreen agents, and to topical sunscreen or cosmetic compositions containing sunscreen agents. [0003] Topical sunscreen products protect the skin from the effects of harmful ultraviolet (UV) radiation by preventing the transmission of that radiation through absorption and scattering processes. A variety of sunscreen agents have been used in such products. One type of sunscreen agent that is widely used is a particulate metal oxide. Titanium dioxide and zinc oxide particles are most commonly used. Sometimes combinations of these are used. [0004] The difficulty with using metal oxides as the active sunscreen agent is that it is difficult to formulate a product that is t...

AI Technical Summary

Benefits of technology

[0029] Suitable M1X compounds for applying a zinc oxide film are diethyl zinc and dimethyl zinc. Suitable M1X compound for applying a titanium dioxide film are titanium tetraisopropoxide and titanium tetraethoxide. Suitable M1X compounds for applying a cerium oxide film are cerium tetramethylheptanedionate and cerium trimethylheptanedionate phenanthroline. In some cases, the corresponding metal halides can be used.

[0030] A reaction scheme for the deposition of TiO2 is described in Tsapatsis et al. (1991) Ind. Eng. Chem. Res. 30:2152-2159 and Lin et al., (1992), AlChE Journal 38:445-454, both incorporated herein by reference.

[0031] In addition, catalyzed binary reaction techniques such as described in copending application Ser. No. 08/942,522 entitled “Method of Growing Films on Substrates at Room Temperatures Using Catalyzed Binary Reaction Sequence Chemistry”, incorporated by reference, are suitable for depositing inorganic materials, especially oxide, nitride or sulfide coatings, most preferably oxide coatings. Reactions of this type can be represented as follows:

[0032] Except for the catalyzed reaction scheme described above, the binary reactions are generally performed at elevated temperatures, preferably from about 300-1000K. Between reactions, the particles are subjected to conditions sufficient to remove reaction products and unreacted reagents. This can be done, for example, by subjecting the particles to a high vacuum, such as about 10−5 Torr or less, after each reaction step. Another method of accomplishing this, which is more readily applicable for industrial application, is to sweep the particles with an inert purge gas between the reaction steps. This purge gas can also act as a fluidizing medium for the particles and as a carrier for the reagents.

[0033] Several techniques are useful for monitoring the progress of the reaction. For example, vibrational spectroscopic studies can be performed on high surface area silica powders using transmission Fourier transform infrared techniques. The deposited inorganic materials can be examined using in situ spectroscopic ellipsometry. Atomic force microscopy studies can be used to characterize the roughness of the coat

Problems solved by technology

The difficulty with using metal oxides as the active sunscreen agent is that it is difficult to formulate a product that is transparent and yet has a high sunscreen protection factor (SPF).

Similarly, many cosmetic products such as foundations are formulated to produce a specific color or tone, but cannot be done so when the metal oxide content is too high.

The organic sunscreen agents are often susceptible to photodegradation and/or chemic